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IBM retained its lead of the Top500 list of supercomputers with its BlueGene/L System installed at the U.S. Department of Energy's (DOE's) Lawrence Livermore National Laboratories in Livermore, California. The system topped the twice-yearly list of the fastest computers in the world for the third consecutive time and is likely to remain No. 1 for some time since its size doubled earlier this year.

The list, the 26th to be issued, was due to be announced Monday at the Supercomputing conference (SC05) taking place in Seattle through Friday.

There was some shakeup among the global top ten supercomputers with new entrants displacing some incumbents on June's list.

Cray notched up one new system and one revamped system, while IBM and Dell had one new system apiece in the top 10. Two IBM eServer Blue Gene systems on June's list dropped off the top 10 -- the Blue Protein supercomputer at the Computational Biology Research Center in Japan and a Blue Gene machine at the Ecole Polytechnique Fédérale de Lausanne in Switzerland. Also exiting the top 10 was the Thunder supercomputer at the Lawrence Livermore laboratory based on Intel's Itanium 2 processors.

IBM's Blue Gene/L was measured with a Linpack benchmark performance of 280.6 teraflops. A teraflop is one trillion mathematical calculations per second.

In second position to the BlueGene/L was IBM's Watson Blue Gene (WBG) eServer system which the company installed at its Thomas J. Watson Research Center in June with a performance of 91.3 teraflops. New in at No. 3 was the ASCI Purple system built by IBM and based on its pSeries 575 server, which is also installed at the Lawrence Livermore lab. It was measured at 63.4 teraflops.

Silicon Graphics' Columbia system at the NASA (National Aeronautics and Space Administration) Ames Research Center in Moffet Field, California, slipped from June's third position to fourth place with 51.9 teraflops.

The DOE's Sandia National Laboratories had two newly installed systems at No. 5 and 6 on the list, Thunderbird, a Dell PowerEdge-based system just edging ahead of Red Storm, a revamped Cray machine with maximum performances of 38.3 teraflops and 36.2 teraflops respectively.

NEC's Earth Simulator in Yokohama, Japan, which topped the Top500 list for five consecutive times until IBM displaced it a year ago, was in seventh position with a performance of 35.9 teraflops, a slip from June's No. 4 position.

In eighth position was another IBM machine, the fastest computer in Europe, the MareNostrum at the Barcelona Supercomputer Center in Spain, with a performance of 27.9 teraflops. The MareNostrum was number five on June's Top500 list. After that came another IBM eServer BlueGene machine, owned by Astron and run at the University of Groningen in the Netherlands with a performance of 27.4 teraflops. In 10th position was another new entry, a Cray machine at the DOE's Oak Ridge National Laboratory in the U.S. with a performance of 20.5 teraflops.

IBM had the most supercomputers on the list with 43.8 percent, followed by Hewlett-Packard, with 33.8 percent of all systems, though the latter had no showing in the top 10 list.

Two-thirds of the Top500 machines are powered by Intel's chips, with 81 of the 333 systems using the chip giant's EM64T-based processors. IBM's Power chips appeared in 73 systems. Intel's rival Advanced Micro Devices (AMD) had processors in 55 systems, more than doubling its standing on the last list put out in June.

Geographically speaking, the U.S. dominates the list, accounting for 305 of the Top500 supercomputers, trailed by Europe with 100 systems and Asia with 66 machines. Germany, which had been the leading European supercomputer country with 40 systems on June's Top500 list, only had 24 systems on the new list. with the U.K. becoming the number-one European player with 41 systems up from June's 32 systems.

The Top500 list was compiled by Erich Strohmaier and Horst Simon of the National Energy Research Scientific Computing Center (NERSC)/Lawrence Berkeley National Laboratory, Hans Meuer of the University of Mannheim, Germany, and Jack Dongarra of the University of Tennessee, Knoxville.

As of Monday 05:01 GMT, the Top500 list can be accessed at http://www.top500.org/.